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and the Abiotic effects of Tides |
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We
use
transects to quantify the interrelations
of organisms as they are distributed throughout
the intertidal zone on the shore. Tidal levels
are a major factor in determining this zonation.
In this file you are invited to examine some of
our data, and create your own transect baseline
studies as well. They may have nothing to do
with tides, but they can serve as an excellent
record which you may use to base measurements
showing change or stability of the ecosystem in
the future Here
are
two other time lapse videos from the top of
the tower. Note the distribution of
harbour seals as the tide level changes: An
interesting exercise is to compare the tidal
heights at several locations around Vancouver
Island. There is a significant difference, with
times as well as tidal ranges varying depending
where the station is located. There are many
factors which determine tide levels, the most
obvious being the stages of the moon and the
position of the sun, but here you can see that
geography has a major role to play as well.
Tidal
Height Predictions for Race Rocks (Pedder
Bay)
Moonrise in the East.
Moon above the tower
Animation
of Tides and Currents in the Strait of Juan
de Fuca
CBC
radio interview with Laura Verhegge on
Negative tides
Close up
4
Images of the moon from the Race Rocks remote cam
5 provided by Pam
Birley.
The Remote Cam 5
has a clear shot of the moonrise. G.Fletcher
photo)
Eclipse
of the moon from Southern Vancouver Island,
February 21, 2008,
photos by Garry Fletcher
Of
course, both the moon and the sun are responsible
for the tides at Race Rocks. We also have this
Solar File which shows the effects of the Sun as
an abiotic factor
ANITA'S
ISLAND:
One has to explore Race Rocks, at least virtually,
in the month of June when the tidal level often
drops below zero datum to really appreciate the
effects of the daily changing tidal levels. The
island above, located on the West side of Great
Race Rock, is actually a peninsula you can walk
out onto when the tides drop to -0.0m, but is
totally submerged at high tide, (around 2.6
meters). You can often see the top of it from
preset 4 on camera1. ( It looks black
because it is covered with mussels.) For several
years now, we have done research with Dr.
Anita Brinckmann-Voss on these low tides in
June. We only have a half hour or so until the
isthmus is flooded however.
THE
INTERTIDAL ZONE:
The
island is totally covered on every square
centimeter with some form of life, either
invertebrate or plant. Those organisms nearer
the top are more resistant to changing
temperatures and changing salinity. (Exposure in
a rain storm means they have to tolerate fresh
water, and changing
salinity) .This
file gives a number of images of the lower
intertidal zone on this side of Great Race
Rock.
RESEARCH
ESSAY:
The
implications for an organism living at different
elevations on the intertidal zone are very
significant. Over the years several students
have done research
essays investigating this feature.
TIDEPOOLS:
In our tidepool
file , you will find an
index with links to a set of tidepools where
we have recorded the effects of the tide being out
for different lengths of time. The abiotic
conditions in the pools change significantly as
the tide levels go up and down.
Salinity and Temperature
are especially variable and they influence the
type of organisms that lives within the pools.
Intertidal
TRANSECT Studies.
Video
of the Tidal Levels at Race Rocks.
Coming
Soon!: With the deployment of the Tidal Current
Generator, a set of sensors for environmental
monitoring will also be deployed. Included will be
a current meter and an ADCP which will be able to
present the variables of tidal events here in
graphical form in real time.. Assistance for our
installation of oceanographic sensors has come
from the BC
Ministry of Mines and Energy.
Other
tidal heights from along the coast of Vancouver
Island and British Columbia
Link
to this file on intertidal exposure due to tidal
variations.
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Contact
Garry
FletcherCopyright